The invention relates to a multinozzle generator for high frequency ventilation of lungs.
The state of the art generator for high frequency nozzle ventilation of lungs comprises a nozzle of a certain nominal internal diameter having the shape of a relatively long tube which engages by its distal end into a cylindrical hollow of an extension of an intubation tube, the nominal internal diameter of which is equal to the nominal internal diameter of the tube. The tube forming the nozzle is situated in the axis of a cylindrical hollow of the extension and is usually fastened in a fitting of a humidifying supply means of gases and the extension of the intubation tube is by its cone inserted into the hollow of the fitting.
These known solutions of similar generators have a number of drawbacks.
In case a nominal internal diameter of the generator nozzle and a different internal diameter of the cylindrical hollow of the extension of the intubation tube are used, a different maximum generator overpressure and a different internal generator resistance are experienced even in case of a uniform insufflation pressure in the nozzle. For instance for a uniform internal diameter of the nozzle in case of a change to a double of the nominal diameter of the cylindrical hollow of the extension an approximately four times change of the maximum generator overpressure and an approximately eight times change of the internal resistance of the generator are obtained. This physical fact makes the programming of high frequency nozzle ventilation difficult and can also cause damages of lungs due to excessive overpressure.
Another drawback of known solutions is the difficulty of an adjustment of the generator to the instantaneous condition of lungs. For instance in case of a supporting nozzle ventilation, where this ventilation is superposed to the breathing activity of the patient, the maximum generator overpressure and the internal generator resistance have to be reduced and the superposed ventilation has to be adjusted to the breathing activity of the patient while maintaining a certain level of the insufflation pressure in the nozzle which induces the dynamic overpressure in the intubation tube. In case the air passages of the patient have a relatively high throughflow resistance, it is necessary to increase the maximum overpressure power of the generator and also to increase its internal resistance, which can only be achieved solely by a substantial increase of the insufflation overpressure, whereby the internal resistance of the generator increases only by about its square root.
A further drawback of known solutions of generators having a nozzle of the shape of a relatively long tube disposed along the axis of a cylindrical hollow or an extension of the intubation tube resides in the limitation of movement of the suction catheter in case the suction of the patient has to be performed without interruption of the ventilation, whereby this possibility of sucking without interruption of the ventilation is one of the advantages of high frequency nozzle ventilation. This advantage is also present in case the state of the art devices are used in connection with a bronchoscope, where the nozzle of the shape of a tube situated within the bronchoscope tube obstructs the optical tubus or an operational tool respectively.
Another drawback in the application of a nozzle of the shape of a relatively long tube resides in the substantial loss of power due to streaming of gases in a long narrowed passage.